1. Field of the Invention
The present invention relates to methods for measuring displacement (i.e. distance and direction moved) of an object, and more particularly, to a method and an apparatus for measuring displacement of an object having a flat surface, the displacement being in a direction normal to the flat surface.
2. Discussion of the Related Art
With the development of technology, products are increasingly being made smaller and lighter. Thus in manufacturing processes, standards for precise manufacturing technology have become more rigorous. Therefore, measuring precise distance and position has become more important. High precision measuring devices and methods have therefore become widely utilized.
In conventional measuring methods, methods using photoelectric remote measuring have many advantages, they avoid the jamming associated with mechanical methods, have large working distances, high measuring precision, high operating speed, and a wide range of application. Out of the various methods of no-contact measurement, remote measuring using optical laser triangulation is most widely utilized due to its simple apparatus and ease of use.
A conventional method of remote measurement using laser optical triangulation mainly consist of a laser source, a lens and a light sensitive transducer. The laser source illuminates an aim point of on the object being measured, and an image point of the aim point is formed on the light sensitive transducer through the lens. As the object moves, the image point moves correspondingly. By measuring the distance that the image point moves, the displacement of the object can be computed.
However, in a measuring process using single point laser optical triangulation, when the object moves two equal distances, the movement distances of the image point are unequal. That is, the measuring method is not linear, thus complicating the calculations. In addition, the measuring precision is effected by the quality of the lens.
What is needed, therefore, is a method for measuring a displacement of an object with an simple algorithm program.